Recently, the standardization for Blu-ray Rewritable (referred to as BD-RE hereinafter), which is a new high-density rewritable optical disk, capable of recording high-quality video and audio data for a long time, is in rapid progress. BD-RE related products will be available on the market when the standardization is completed.
The data recording layer of a single-layered BD-RE disk is located at a distance of 0.1 mm from the disk surface in the direction normal to an objective lens 11 contained in an optical pickup, as illustrated in FIG. 1.
For recording/reproducing data on/from the recording layer of the BD-RE, the laser power of a laser diode (LD) 13 contained in the optical pickup is adjusted according to the operation mode, which will be described in detail below.
FIG. 2 shows a table of disk information recorded in the lead-in area of a conventional single-layered BD-RE. The lead-in area comprises a pre-recorded area and a rewritable area and the pre-recorded area includes a PIC (Permanent Information & Control) data zone.
As illustrated in FIG. 2, information such as the disk information ID, the disk structure, a maximum DC read power and a maximum high-frequency modulated read power for adjusting read power is recorded in the PIC data zone.
Also, write power settings at a normal recording velocity, write power settings at a maximum recording velocity, and write power settings at a minimum recording velocity for adjusting write power are recorded in the PIC data zone.
An optical disk apparatus in which the BD-RE having the information shown in FIG. 2 is placed adjusts the amount of the current that flows through the LD contained in the optical pickup optimal to the present operation mode by referring to the disk information stored in the PIC data zone before beginning to reproduce data recorded on the recording layer of the BD-RE or to record data on the recording layer of the ED-RE.
On the other hand, dual-layered BD-RE disks having a storage capacity twice as much as that of a single-layered BD-RE disk have been proposed. A dual-layered BD-RE has two recording layers, Layer 1 and Layer 2, located at a prescribed distance (d2) away from each other, as illustrated in FIG. 3.
The optical power of the LD 13 needs to be adjusted appropriately for recording data on a selected layer or reproducing data from a layer in the same way as the case for a single-layered disk. If optical power related information only for either of the layers is recorded or an identical optical power is employed for both layers, the recording/reproducing performance is likely to be deteriorated on one of the two layers. For example, suppose that an optical read power set appropriately for Layer 1 is used to read data recorded on Layer 2. A portion of the laser beam reflected by Layer 2 is reflected again by Layer 1 located below. Also, a portion of the laser beam created by the LD 13 is reflected by Layer 1 before reaching Layer 2, which results in an optical loss. For these reasons, the data recorded on Layer 2 may not be read successfully, though data reproduction from Layer 1 is successful.
As a result, it is required to maintain optical power related information for each of the recording layers separately. Optical power related data for Layer 1 is recorded in the lead-in area of Layer 1 and optical power related data for Layer 2 is recorded in the lead-out area of Layer 2. When jumping from Layer 1 to Layer 2 in the middle of a reproducing/reading operation on Layer 1, the reproducing/reading operation on Layer 2 cannot start immediately after the jump. Rather, there is a delay until the optical power related information recorded on the lead-out area of Layer 2 is accessed.